Tissue ablation apparatus

ABSTRACT

A tissue ablation apparatus comprises a first elongated delivery device including a lumen and an obturator with a tissue piercing distal end. The obturator is positionable in the lumen of the first elongated delivery device. A second elongated delivery device is positionable in the lumen of the first elongated delivery device. An energy delivery device is positionable in the second elongated delivery device. The energy delivery device includes at least a first and a second RF electrode each with a tissue piercing distal portion. The first and second RF electrodes are positionable in the second elongated delivery device in a compacted state and deployable from the second elongated delivery device with curvature in a deployed state. The first and second RF electrodes exhibit a changing direction of travel when advanced from the second elongated delivery device to a selected tissue site. At least one infusion port is coupled to one of the first elongated delivery device, the second elongated delivery device, the energy delivery device, the first RF electrode or the second RF electrode. An electrode advancement member is coupled to the first and second RF electrodes. The advancement member is configured to advance the RF electrode out of the elongated delivery device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 09/383,166 filedAug. 25, 1999 now U.S. Pat. No. 6,471,698 which is a continuation ofU.S. Ser. No. 08/802,195, filed Feb. 14, 1997, now U.S. Pat. No.6,071,280, which is a continuation-in-part of application Ser. No.08/515,379, filed Aug. 15, 1995, now U.S. Pat. No. 5,683,384 which is acontinuation-in-part of U.S. patent application Ser. No. 08/290,031,filed Aug. 12, 1994, now U.S. Pat. No. 5,536,267 which is acontinuation-in-part of U.S. patent application Ser. No. 08/148,439,filed Nov. 8, 1993, now U.S. Pat. No. 5,458,597, each of which isincorporated by reference herein. This application is also acontinuation of application Ser. No. 09/364,203, filed Jul. 30, 1999 nowU.S. Pat No. 5,466,177, which is a continuation of application Ser. No.08/623,652, filed Mar. 29, 1996, now U.S. Pat. No. 5,935,123, which is adivisional of application Ser. No. 08/295,166, filed Aug. 24, 1994, nowU.S. Pat. No. 5,599,345, which is a continuation-in-part of applicationSer. No. 08/148,439, filed Nov. 8, 1993, now U.S. Pat. No. 5,458,597,each of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an apparatus for the treatment andablation of body masses, such as tumors, and more particularly, to an RFtreatment system suitable for multi-modality treatment with an infusiondelivery and a retractable multiple needle electrode apparatus thatsurrounds an exterior of a tumor with a plurality of needle electrodesand defines an ablative volume. The system maintains a selected power atan electrode that is independent of changes in current or voltage.

2. Description of Related Art

Current open procedures for treatment of tumors are extremely disruptiveand cause a great deal of damage to healthy tissue. During the surgicalprocedure, the physician must exercise care in not cutting the tumor ina manner that creates seeding of the tumor, resulting in metastasis. Inrecent years development of products has been directed with an emphasison minimizing the traumatic nature of traditional surgical procedures.

There has been a relatively significant amount of activity in the areaof hyperthermia as a tool for treatment of tumors. It is known thatelevating the temperature of tumors is helpful in the treatment andmanagement of cancerous tissues. The mechanisms of selective cancer celleradication by hyperthermia are not completely understood. However, fourcellular effects of hyperthermia on cancerous tissue have been proposed,(i) changes in cell or nuclear membrane permeability or fluidity, (ii)cytoplasmic lysomal disintegration, causing release of digestiveenzymes, (iii) protein thermal damage affecting cell respiration and thesynthesis of DNA or RNA and (iv) potential excitation of immunologicsystems. Treatment methods for applying heat to tumors include the useof direct contact radio-frequency (RF) applicators, microwave radiation,inductively coupled RF fields, ultrasound, and a variety of simplethermal conduction techniques.

Among the problems associated with all of these procedures is therequirement that highly localized heat be produced at depths of severalcentimeters beneath the surface of the body. Certain techniques havebeen developed with microwave radiation and ultrasound to focus energyat various desired depths. RF applications may be used at depth duringsurgery. However, the extent of localization is generally poor, with theresult that healthy tissue may be harmed. Induction heating gives riseto poor localization of the incident energy as well. Although inductionheating may be achieved by placing an antenna on the surface of thebody, superficial eddy currents are generated in the immediate vicinityof the antenna. When it is driven using RF current unwanted surfaceheating occurs diminishing heating to the underlying tissue.

Thus, non-invasive procedures for providing heat to internal tumors havehad difficulties in achieving substantial specific and selectivetreatment.

Hyperthermia, which can be produced from an RF or microwave source,applies heat to tissue but does not exceed 45 degrees C. so that normalcells survive. In thermotherapy, heat energy of greater than 45 degreesC. is applied, resulting in histological damage, desiccation and thedenaturization of proteins. Hyperthermia has been applied more recentlyfor therapy of malignant tumors. In hyperthermia, it is desirable toinduce a state of hyperthermia that is localized by interstitial currentheating to a specific area while concurrently insuring minimum thermaldamage to healthy surrounding tissue. Often, the tumor is locatedsubcutaneously and addressing the tumor requires either surgery,endoscopic procedures or external radiation. It is difficult toexternally induce hyperthermia in deep body tissue because currentdensity is diluted due to its absorption by healthy tissue.Additionally, a portion of the RF energy is reflected at the muscle/fatand bone interfaces which adds to the problem of depositing a knownquantity of energy directly on a small tumor. Attempts to useinterstitial local hyperthermia have not proven to be very successful.Results have often produced nonuniform temperatures throughout thetumor. It is believed that tumor mass reduction by hyperthermia isrelated the thermal dose. Thermal dose is the minimum effectivetemperature applied throughout the tumor mass for a defined period oftime. Because blood flow is the major mechanism of heat loss for tumorsbeing heated, and blood flow varies throughout the tumor, more evenheating of tumor tissue is needed to ensure more effective treatment.

The same is true for ablation of the tumor itself through the use of RFenergy. Different methods have been utilized for the RF ablation ofmasses such as tumors. Instead of heating the tumor it is ablatedthrough the application of energy. This process has been difficult toachieve due to a variety of factors including, (i) positioning of the RFablation electrodes to effectively ablate all of the mass, (ii)introduction of the RF ablation electrodes to the tumor site and (iii)controlled delivery and monitoring of RF energy to achieve successfulablation without damage to non-tumor tissue.

There have been a number of different treatment methods and devices forminimally invasively treating tumors. One such example is an endoscopethat produces RF hyperthermia in tumors, as disclosed in U.S. Pat. No.4,920,978. A microwave endoscope device is described in U.S. Pat. No.4,409,993. In U.S. Pat. No. 4,920,978, an endoscope for RF hyperthermiais disclosed.

In U.S. Pat. No. 4,763,671, a minimally invasive procedure utilizes twocatheters that are inserted interstitially into the tumor. The cathetersare placed within the tumor volume and each is connect to a highfrequency power source.

In U.S. Pat. No. 4,565,200, an electrode system is described in which asingle entrance tract cannula is used to introduce an electrode into aselected body site.

However, as an effective treatment device, electrodes must be properlypositioned relative to the tumor. After the electrodes are positioned,it is then desirable to have controlled application and deposition of RFenergy to ablate the tumor. This reduces destruction of healthy tissue.

There is a need for a RF tumor treatment apparatus that is useful forminimally invasive procedures. It would be desirable for such a deviceto surround the exterior of the tumor with treatment electrodes,defining a controlled ablation volume, and subsequently the electrodesdeliver a controlled amount of RF energy. Additionally, there is a needfor a device with infusion capabilities during a pre-ablation step, andafter ablation the surrounding tissue can be preconditioned withelectromagnetic (“EM”) energy at hyperthermia temperatures less than 45degrees. This would provide for the synergistic affects of chemotherapyand the instillation of a variety of fluids at the tumor site afterlocal ablation and hyperthermia.

SUMMARY OF THE INVENTION

In an embodiment of the invention, a tissue ablation apparatus comprisesa first elongated delivery device including a lumen and an obturatorwith a tissue piercing distal end. The obturator is positionable in thelumen of the first elongated delivery device. A second elongateddelivery device is positionable in the lumen of the first elongateddelivery device. An energy delivery device is positionable in the secondelongated delivery device. The energy delivery device includes at leasta first and a second RF electrode each with a tissue piercing distalportion. The first and second RF electrodes are positionable in thesecond elongated delivery device in a compacted state and deployablefrom the second elongated delivery device with curvature in a deployedstate. The first and second RF electrodes exhibit a changing directionof travel when advanced from the second elongated delivery device to aselected tissue site. At least one infusion port is coupled to one ofthe first elongated delivery device, the second elongated deliverydevice, the energy delivery device, the first RF electrode or the secondRF electrode. An electrode advancement member is coupled to the firstand second RF electrodes. The advancement member is configured toadvance the RF electrode out of the elongated delivery device.

In another embodiment, a tissue ablation apparatus includes a deliverycatheter, with distal and proximal ends. A handle is attached to theproximal end of the delivery catheter. An electrode deployment apparatusis positioned at least partially in the delivery catheter. It includes aplurality of electrodes that are retractable in and out of thecatheter's distal end. The electrodes are in a non-deployed state whenthey are positioned within the delivery catheter. As they are advancedout the distal end of the catheter they become deployed, and define anablation volume. Each electrode has a first section with a first radiusof curvature, and a second section, extending beyond the first section,having a second radius of curvature or a substantially linear geometry.Alternatively, each deployed electrode has at least two radii ofcurvature that are formed when the needle is advanced through thedelivery catheter's distal end and becomes positioned at a selectedtissue site. Also each deployed electrode can have at least one radiusof curvature in two or more planes. Further, the electrode deploymentapparatus can include at least one deployed electrode having at leastradii of curvature, and at least one deployed electrode with at leastone radius of curvature in two or more planes.

In a further embodiment, the electrode deployment apparatus has at leastone deployed electrode with at least one curved section that is locatednear the distal end of the delivery catheter, and a non-curved sectionwhich extends beyond the curved section of the deployed electrode. Theelectrode deployment apparatus also has at least one deployed electrodewith at least two radii of curvature.

In another embodiment of the invention, each deployed electrode has atleast one curved section located near the distal end of the deliverycatheter, and a non-curved section that extends beyond the curvedsection of the deployed electrode.

An electrode template can be positioned at the distal end of thedelivery catheter. It assists in guiding the deployment of theelectrodes to a surrounding relationship at an exterior of a selectedmass in a tissue. The electrodes can be hollow. An adjustable electrodeinsulator can be positioned in an adjacent, surrounding relationship toall or some of the electrodes. The electrode insulator is adjustable,and capable of being advanced and retracted along the electrodes inorder to define an electrode conductive surface.

The electrode deployment apparatus can include a cam which advances andretracts the electrodes in and out of the delivery catheter's distalend. Optionally included in the delivery catheter are one or more guidetubes associated with one or more electrodes. The guide tubes arepositioned at the delivery catheter's distal end.

Sources of infusing mediums, including but not limited to electrolyticand chemotherapeutic solutions, can be associated with the hollowelectrodes. Electrodes can have sharpened, tapered ends in order toassist their introduction through tissue, and advancement to theselected tissue site.

The electrode deployment apparatus is removable from the deliverycatheter. An obturator is initially positioned within the deliverycatheter. It can have a sharpened distal end. The delivery catheter canbe advanced percutaneously to an internal body organ, or site, with theobturator positioned in the delivery catheter. Once positioned, theobturator is removed, and the electrode deployment apparatus is insertedinto the delivery catheter. The electrodes are in non-deployed states,and preferably compacted or spring-loaded, while positioned within thedelivery catheter. They are made of a material with sufficient strengthso that as the electrodes emerge from the delivery catheter's distal endthey are deployed three dimensionally, in a lateral direction away fromthe periphery of the delivery catheter's distal end. The electrodescontinue their lateral movement until the force applied by the tissuecauses the needles to change their direction of travel.

Each electrode now has either, (i) a first section with a first radiusof curvature, and a second section, extending beyond the first section,having a second radius of curvature or a substantially linear section,(ii) two radii of curvature, (iii) one radius of curvature in two ormore planes, or (iv) a combination of two radii of curvature with one ofthem in two or more planes. Additionally, the electrode deploymentapparatus can include one or more of these deployed geometries for thedifferent electrodes in the plurality. It is not necessary that everyelectrode have the same deployed geometry.

After the electrodes are positioned around a mass, such as a tumor, avariety of solutions, including but not limited to electrolytic fluids,can be introduced through the electrodes to the mass in a pre-ablationstep. RF energy is applied, and the mass is desiccated. In apost-ablation procedure, a chemotherapeutic agent can then be introducedto the site, and the electrodes are then retracted back into theintroducing catheter. The entire ablative apparatus can be removed, oradditional ablative treatments be conducted.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of the tissue ablation apparatus of theinvention, including a delivery catheter, handle, and deployedelectrodes.

FIG. 2 is a cross-sectional view of the tissue ablation apparatus of theinvention illustrated in FIG. 1.

FIG. 3 is a perspective view of an electrode of the invention with tworadii of curvature.

FIG. 4 is a perspective view of an electrode of the invention with oneradius of curvature in three planes.

FIG. 5 is a perspective view of an electrode of the invention with onecurved section, positioned close to the distal end of the deliverycatheter, and a linear section.

FIG. 6 is a perspective view of an electrode of the invention with onecurved section, positioned close to the distal end of the deliverycatheter, a generally first linear section, and then a second linearsection that continues laterally with regard to the first linearsection.

FIG. 7 is a cross-section view of a delivery catheter associated withthe invention, with guide tubes positioned at the distal end of thedelivery catheter.

FIG. 8 is a cross-sectional view of an electrode of the invention.

FIG. 9 is a perspective view of the tissue ablation apparatus of theinvention shown in FIG. 1, with the delivery catheter being introducedpercutaneously through the body and positioned at the exterior, orslightly piercing, a liver with a tumor to be ablated.

FIG. 10 is a perspective view of the tissue ablation apparatus of theinvention with an obturator positioned in the delivery catheter.

FIG. 11 is a perspective view of the tissue ablation apparatus of theinvention shown in FIG. 10, positioned in the body adjacent to theliver, with the obturator removed.

FIG. 12 is a perspective view of the tissue ablation apparatus of theinvention shown in FIG. 10, positioned in the body adjacent to theliver, and the electrode deployment apparatus, with an electrodetemplate, is positioned in the delivery catheter in place of theobturator.

FIG. 13 is a perspective view of the ablation apparatus of theinvention, with deployed electrodes surrounding a tumor and defining anablation volume.

FIG. 14 is a perspective view of the tissue ablation apparatus of theinvention shown in FIG. 10, positioned in the body adjacent to theliver, with deployed electrodes surrounding a tumor and infusing asolution to the tumor site during a pre-ablation procedure.

FIG. 15 is a perspective view of the tissue ablation apparatus of theinvention shown in FIG. 10, illustrating application of RF energy to thetumor.

FIG. 16 is a perspective view of the tissue ablation apparatus of theinvention, illustrating the electro-desiccation of the tumor.

FIG. 17 is a perspective view of the tissue ablation apparatus of theinvention, illustrating the instillation of solutions to the tumor siteduring a post-ablation procedure.

FIG. 18 illustrates bipolar ablation between electrodes of theinvention.

FIG. 19 illustrates monopolar ablation between electrodes of theinvention.

FIG. 20 is a perspective view of an ablation system of the invention,including RF and ultrasound modules, and a monitor.

FIG. 21 is a block diagram of the ablation system of the invention.

FIG. 22(a) is a cross-sectional view of an RF treatment apparatus of theinvention.

FIG. 22(b) is a close up cross-sectional view of the distal end of theRF treatment apparatus of FIG. 22(a).

FIG. 22(c) is a close up cross-sectional view of the RF treatmentapparatus of FIG. 22(a), illustrating the proximal end of the insulationsleeve and a thermocouple associated with the insulation sleeve.

FIG. 22(d) is a close up cross-sectional view of the RF treatmentapparatus of FIG. 22(a), illustrating the proximal end of the RFtreatment apparatus of FIG. 22(a).

FIG. 23 is an exploded view of an RF treatment apparatus of theinvention.

FIG. 24 is a cross-sectional view of the RF treatment apparatus of theinvention illustrating the electrode, insulation sleeve and theassociated thermal sensors.

FIG. 25(a) is a perspective view of the RF treatment apparatus of theinvention with the infusion device mounted at the distal end of thecatheter.

FIG. 25b is a perspective view of the RF treatment apparatus of FIG.25(a) illustrating the removal of the catheter, and electrode attachedto the distal end of the electrode, from the infusion device which isleft remaining in the body.

FIG. 26(a) is a perspective view of the RF treatment apparatus of theinvention with the electrode mounted at the distal end of the catheter.

FIG. 26(b) is a perspective view of the RF treatment apparatus of FIG.26(a) illustrating the removal of the introducer from the lumen of theelectrode.

FIG. 27(a) is a perspective view of the RF treatment apparatus of theinvention with the introducer removed from the lumen of the electrode.

FIG. 27(b) is a perspective view of the apparatus of FIG. 27(a)illustrating the removal of the electrode from the catheter, leavingbehind the insulation sleeve.

FIG. 28(a) is a perspective view of the RF ablation apparatus of theinvention with the insulation sleeve positioned in a surroundingrelationship to the electrode which is mounted to the distal end of thecatheter.

FIG. 28(b) is a perspective view of the RF ablation apparatus of FIG.28(a) illustrating the removal of the insulation sleeve from theelectrode.

FIG. 28(c) is a perspective view of the insulation sleeve after it isremoved from the electrode.

FIG. 29(a) is a perspective view illustrating the attachment of asyringe to the device of FIG. 27(a).

FIG. 29(b) is a perspective view of a syringe, containing a fluid mediumsuch as a chemotherapeutic agent, attached to the RF ablation apparatusof FIG. 27(a).

FIG. 30 is a block diagram of an RF treatment system of the invention.

FIG. 31 is a block diagram of an embodiment of the invention whichincludes a microprocessor.

FIG. 32 illustrates the use of two RF treatment apparatus, such as theone illustrated in FIG. 22(a), that are used in a bipolar mode.

DETAILED DESCRIPTION

A tissue ablation apparatus 10 of the invention is illustrated in FIG.1. Ablation apparatus 10 includes a delivery catheter 12, well known tothose skilled in the art, with a proximal end 14 and a distal end 16.Delivery catheter 12 can be of the size of about 5 to 16 F. A handle 18is removably attached to proximal end 14. An electrode deployment deviceis at least partially positioned within delivery catheter 12, andincludes a plurality of electrodes 20 that are retractable in and out ofdistal end 16. Electrodes 20 can be of different sizes, shapes andconfigurations. In one embodiment, they are needle electrodes, withsizes in the range of 27 to 14 gauge. Electrodes 20 are in non-deployedpositions while retained in delivery catheter. In the non-deployedpositions, electrodes 20 may be in a compacted state, spring loaded,generally confined or substantially straight if made of a suitablememory metal such as nitinol. As electrodes 20 are advanced out ofdistal end 16 they become distended in a deployed state, which definesan ablative volume, from which tissue is ablated as illustrated morefully in FIG. 2. Electrodes 20 operate either in the bipolar ormonopolar modes. When the electrodes are used in the bipolar mode, theablative volume is substantially defined by the peripheries of theplurality of electrodes 20. In one embodiment, the cross-sectional widthof the ablative volume is about 4 cm. However, it will be appreciatedthat different ablative volumes can be achieved with tissue ablationapparatus 10.

The ablative volume is first determined to define a mass, such as atumor, to be ablated. Electrodes 20 are placed in a surroundingrelationship to a mass or tumor in a predetermined pattern forvolumetric ablation. An imaging system is used to first define thevolume of the tumor or selected mass. Suitable imaging systems includebut are not limited to, ultrasound, computerized tomography (CT)scanning, X-ray film, X-ray fluoroscopy, magnetic resonance imaging,electromagnetic imaging, and the like. The use of such devices to definea volume of a tissue mass or a tumor is well known to those skilled inthe art.

With regard to the use of ultrasound, an ultrasound transducer transmitsultrasound energy into a region of interest in a patient's body. Theultrasound energy is reflected by different organs and different tissuetypes. Reflected energy is sensed by the transducer, and the resultingelectrical signal is processed to provide an image of the region ofinterest. In this way, the ablation volume is then ascertained, and theappropriate electrode deployment device is inserted into deliverycatheter 12.

The ablative volume is substantially defined before ablation apparatus10 is introduced to an ablative treatment position. This assists in theappropriate positioning of ablation apparatus 10. In this manner, thevolume of ablated tissue is reduced and substantially limited to adefined mass or tumor, including a certain area surrounding such atumor, that is well controlled and defined. A small area around thetumor is ablated in order to ensure that all of the tumor is ablated.

With reference again to FIG. 2, electrode sections 20(a) are in deployedstates when they are introduced out of distal end 16. Althoughelectrodes 20 are generally in a non-distended configuration in thenon-deployed state while positioned in delivery catheter 12, they canalso be distended. Generally, electrode sections 20(b) are in retainedpositions while they are non-deployed. This is achieved by a variety ofmethods including but not limited to, (i) the electrodes are pre-sprung,confined in delivery catheter 12, and only become sprung (expanded) asthey are released from delivery catheter 12, (ii) the electrodes aremade of a memory metal, as explained in further detail below, (iii) theelectrodes are made of a selectable electrode material which gives theman expanded shape outside of delivery catheter 12, or (iv) deliverycatheter 12 includes guide tubes which serve to confine electrodes 12within delivery catheter 12 and guide their direction of travel outsideof the catheter to form the desired, expanded ablation volume. As shownin FIG. 2, electrodes 20 are pre-sprung while retained in deliverycatheter 12. This is the non-deployed position. As they are advanced outof delivery catheter 12 and into tissue, electrodes 20 become deployedand begin to “fan” out from distal end 16, moving in a lateral directionrelative to a longitudinal axis of delivery catheter 12. As deployedelectrodes 20 continue their advancement, the area of the fan increasesand extends beyond the diameter of distal end 16.

Significantly, each electrode 20 is distended in a deployed position,and collectively, the deployed electrodes 20 define a volume of tissuethat will be ablated. As previously mentioned, when it is desired toablate a tumor, either benign or malignant, it is preferable to ablatean area that is slightly in excess to that defined by the exteriorsurface of the tumor. This improves the chances that all of the tumor iseradicated.

Deployed electrodes 20 can have a variety of different deployedgeometries including but not limited to, (i) a first section with afirst radius of curvature, and a second section, extending beyond thefirst section, having a second radius of curvature or a substantiallylinear geometry, (ii) at least two radii of curvature, (iii) at leastone radius of curvature in two or more planes, (iv) a curved section,with an elbow, that is located near distal end 16 of delivery catheter,and a non-curved section that extends beyond the curved section, or (v)a curved section near distal end 16, a first linear section, and thenanother curved section or a second linear section that is angled withregard to the first linear section. Deployed electrodes 20 need not beparallel with respect to each other. The plurality of deployedelectrodes 20, which define a portion of the needle electrode deploymentdevice, can all have the same deployed geometries, i.e., all with atleast two radii of curvature, or a variety of geometries, i.e., one withtwo radii of curvature, a second one with one radius of curvature in twoplanes, and the rest a curved section near distal end 16 of deliverycatheter 12 and a non-curved section beyond the curved section.

A cam 22, or other actuating device, can be positioned within deliverycatheter and used to advance and retract electrodes 20 in and out ofdelivery catheter 12. The actual movement of cam can be controlled athandle 18. Suitable cams are of conventional design, well known to thoseskilled in the art.

The different geometric configurations of electrodes 20 are illustratedin FIGS. 3 through 6. In FIG. 3, electrode 20 has a first radius ofcurvature 20(c) and a second radius of curvature 20(d). It can includemore than two radii of curvature. As shown in FIG. 4, electrode 20 hasat least one radius of curvature which extends to three planes. In FIG.5, each electrode has a first curved section 20(e) which is near distalend 16 of delivery catheter 12. A first generally linear section 20(f)extends beyond curved section 20(e), and the two meet at an elbow 20(g).The electrodes 20 can serve as anodes and cathodes. The plurality ofelectrodes 20 can have linear sections 20(f) that are generally parallelto each other, or they can be non-parallel. FIG. 6 illustrates anelectrode 20 that includes a first curved section 20(e) positioned neardistal end 16 of delivery catheter 12, a first linear section 20(f), anda second linear section 20(h) which extends beyond first linear section20(f). Section 20(h) can be linear, curved, or a combination of the two.The plurality of electrodes 20 illustrated in FIG. 6 can have parallelor non-parallel first linear sections 20(f).

In one embodiment of the invention, electrodes 20 are spring-loaded, andcompacted in their non-deployed positions. As electrodes 20 are advancedout of distal end 16 of delivery catheter 12, they become deployed andfan out. Electrodes 20 continue this fanning out direction until theresistance of the tissue overcomes the strength of the material formingelectrode 20. This causes electrode 20 to bend and move in a directioninward relative to its initial outward fanning direction. The bendingcreates curved sections 20(c) and 20(d) of FIG. 3, and can also resultin the formation of the other electrode 20 geometries of FIGS. 4, 5 and6. The extent of electrode 20 fan like travel is dependent on thestrength of the material from which it is made. Suitable electrodematerials include stainless steel, platinum, gold, silver, copper andother electromagnetic conducting materials including conductivepolymers. Preferably, electrode 20 is made of stainless steel or nickeltitanium and has dimensions of about 27 to 14 gauge.

In one embodiment, electrode 20 is made of a memory metal, such asnickel titanium, commercially available from Raychem Corporation, MenloPark, Calif. Additionally, a resistive heating element can be positionedin an interior lumen of electrode 20. Resistive heating element can bemade of a suitable metal that transfers heat to electrode 20, causingdeployed electrode 20 to become deflected when the temperature ofelectrode 20 reaches a level that causes the electrode material, such asa memory metal, to deflect, as is well known in the art. Not all ofelectrode 20 need be made of a memory metal. It is possible that onlythat distal end portion of electrode 20, which is introduced intotissue, be made of the memory metal in order to effect the desireddeployed geometrical configuration. Additionally, mechanical devices,including but not limited to steering wires, can be attached to thedistal end of electrode 20 to cause it to become directed, deflected andmove about in a desired direction about the tissue, until it reaches itsfinal resting position to ablate a tissue mass.

Optionally included in the delivery catheter are one or more guide tubes24, FIG. 7, which serve to direct the expansion of electrodes 20 in thefan pattern as they are advanced out of distal end 16 of the deliverycatheter 12. Guide tubes 24 can be made of stainless steel, spring steeland thermal plastics including but not limited to nylon and polyesters,and are of sufficient size and length to accommodate the electrodes to aspecific site in the body.

FIG. 8 illustrates one embodiment of electrode 20 with a sharpeneddistal end 24. By including a tapered, or piercing end 24, theadvancement of electrode 20 through tissue is easier. Electrode 20 canbe segmented, and include a plurality of fluid distribution ports 26,which can be evenly formed around all or only a portion of electrode 20.Fluid distribution ports 26 are formed in electrode 20 when it is hollowand permit the introduction and flow of a variety of fluidic mediumsthrough electrode 20 to a desired tissue site. Such fluidic mediumsinclude, but are not limited to, electrolytic solutions, pastes or gels,as well as chemotherapeutic agents. Examples of suitable conductive gelsare carboxymethyl cellulose gels made from aqueous electrolyte solutionssuch as physiological saline solutions, and the like.

The size of fluid distribution ports 26 can vary, depending on the sizeand shape of electrode 20. Also associated with electrode 20 is anadjustable insulator sleeve 28 that is slidable along an exteriorsurface of electrode 20. Insulator sleeve 28 is advanced and retractedalong electrode 20 in order to define the size of a conductive surfaceof electrode 20. Insulator sleeve 28 is actuated at handle 18 by thephysician, and its position along electrode 20 is controlled. Whenelectrode 20 moves out of delivery catheter 12 and into tissue,insulator sleeve 28 can be positioned around electrode 20 as it movesits way through the tissue. Alternatively, insulator sleeve 28 can beadvanced along a desired length of electrode 20 after electrode 20 hasbeen positioned around a targeted mass to be ablated. Insulator sleeveis thus capable of advancing through tissue along with electrode 20, orit can move through tissue without electrode 20 providing the source ofmovement. Thus, the desired ablation volume is defined by deployedelectrodes 20, as well as the positioning of insulator sleeve 28 on eachelectrode. In this manner, a very precise ablation volume is created.Suitable materials that form insulator sleeve include but are notlimited to nylon, polyimides, other thermoplastics, and the like.

The apparatus may further be configured such that the plurality of RFelectrodes include separate infusion lumens with independent fluiddelivery. In this embodiment, the RF electrodes have separate infusionlumens terminating in separate infusion ports. The infusion lumens areone of fluidically or electrically isolated from each other. In afurther embodiment, the elongated delivery device is configured toinclude an infusion lumen that terminates in an infusion port.

FIG. 9 illustrates a percutaneous application of tissue ablationapparatus 10. Tissue ablation apparatus 10 can be used percutaneously tointroduce electrodes 20 to the selected tissue mass or tumor. Electrodes20 can remain in their non-deployed positions while being introducedpercutaneously into the body, and delivered to a selected organ whichcontains the selected mass to be ablated. Delivery catheter 12 isremovable from handle 18. When it is removed, electrode deploymentdevice (the plurality of electrodes 20) can be inserted and removed fromdelivery catheter 12. An obturator 30 is inserted into delivery catheter12 initially if a percutaneous procedure is to be performed. As shown inFIG. 10, obturator 30 can have a sharpened distal end 32 that piercestissue and assists the introduction of delivery catheter 12 to aselected tissue site. The selected tissue site can be a body organ witha tumor or other mass, or the actual tumor itself.

Obturator 30 is then removed from delivery catheter 12 (FIG. 11).Electrode deployment device is then inserted into delivery catheter 12,and the catheter is then reattached to handle 18 (FIG. 12). Asillustrated in FIG. 12, electrode deployment device can optionallyinclude an electrode template 34 to guide the deployment of electrodes20 to a surrounding relationship at an exterior of a selected mass inthe tissue.

Electrodes 20 are then advanced out of distal end 16 of deliverycatheter 12, and become deployed to form a desired ablative volume whichsurrounds the mass. In FIG. 13, delivery catheter 12 is positionedadjacent to the liver. Electrode deployment device is introduced intodelivery catheter 12 with electrode template 34. Electrode deploymentdevice now pierces the liver, and cam 22 advances electrodes 20 out ofdelivery catheter 12 into deployed positions. Each individual electrode20 pierces the liver and travels through it until it is positioned in asurrounding relationship to the tumor. The ablative volume isselectable, and determined first by imaging the area to be ablated. Theablative volume is defined by the peripheries of all of the deployedelectrodes 20 that surround the exterior of the tumor. Once the volumeof ablation is determined, then an electrode set is selected which willbecome deployed to define the ablation volume. A variety of differentfactors are important in creating an ablation volume. Primarily,different electrodes 20 will have various degrees of deployment, basedon type of electrode material, the level of pre-springing of theelectrodes and the geometric configuration of the electrodes in theirdeployed states. Tissue ablation apparatus 10 permits differentelectrode 20 sets to be inserted into delivery catheter 12, in order todefine a variety of ablation volumes.

Prior to ablation of the tumor, a pre-ablation step can be performed. Avariety of different solutions, including electrolytic solutions such assaline, can be introduced to the tumor site, as shown in FIG. 14. FIG.15 illustrates the application of RF energy to the tumor. Electrodeinsulator 28 is positioned on portions of electrodes 20 where there willbe no ablation. This further defines the ablation volume. The actualelectro-desiccation of the tumor, or other targeted masses or tissues,is shown in FIG. 16. Again, deployed electrodes 20, with their electrodeinsulators 28 positioned along sections of the electrodes, define theablation volume, and the resulting amount of mass that is desiccated.

Optionally following desiccation, electrodes 20 can introduce a varietyof solutions in a post-ablation process. This step is illustrated inFIG. 17. Suitable solutions include but are not limited tochemotherapeutic agents.

FIG. 8 illustrates tissue ablation apparatus 10 operated in a bipolarmode. Its monopolar operation is shown in FIG. 19. Each of the pluralityof electrodes 20 can play different roles in the ablation process. Therecan be polarity shifting between the different electrodes.

A tissue ablation system 36, which can be modular, is shown in FIG. 20and can include a display 38. Tissue ablation system 36 can also includean RF energy source, microwave source, ultrasound source, visualizationdevices such as cameras and VCR's, electrolytic and chemotherapeuticsolution sources, and a controller which can be used to monitortemperature or impedance. One of the deployed electrodes 20 can be amicrowave antenna coupled to a microwave source. This electrode caninitially be coupled to RF power source 42 and is then switched to themicrowave source.

Referring now to FIG. 21, a power supply 40 delivers energy into RFpower generator (source) 42 and then to electrodes 20 of tissue ablationapparatus 10. A multiplexer 46 measures current, voltage and temperature(at numerous temperature sensors which can be positioned on electrodes20). Multiplexer 46 is driven by a controller 48, which can be a digitalor analog controller, or a computer with software. When controller 48 isa computer, it can include a CPU coupled through a system bus. Thissystem can include a keyboard, disk drive, or other non-volatile memorysystems, a display, and other peripherals, as known in the art. Alsocoupled to the bus are a program memory and a data memory.

An operator interface 50 includes operator controls 52 and display 38.Controller 48 is coupled to imaging systems, including ultrasoundtransducers, temperature sensors, and viewing optics and optical fibers,if included.

Current and voltage are used to calculate impedance. Diagnostics aredone through ultrasound, CT scanning, or other methods known in the art.Imaging can be performed before, during and after treatment.

Temperature sensors measure voltage and current that is delivered. Theoutput of these sensors is used by controller 48 to control the deliveryof RF power. Controller 48 can also control temperature and power. Theamount of RF energy delivered controls the amount of power. A profile ofpower delivered can be incorporated in controller 38, as well as apre-set amount of energy to be delivered can also be profiled.

Feedback can be the measurement of impedance or temperature, and occurseither at controller 48 or at electromagnetic energy source 42, e.g., RFor microwave, if it incorporates a controller. For impedancemeasurement, this can be achieved by supplying a small amount ofnon-ablation RF energy. Voltage and current are then measured.

Circuitry, software and feedback to controller 48 result in processcontrol and are used to change, (i) power, including RF, ultrasound, andthe like, (ii) the duty cycle (on-off and wattage), (iii) monopolar orbipolar energy delivery, (iv) and electrolytic solution delivery, flowrate and pressure and (v) determine when ablation is completed throughtime, temperature and/or impedance. These process variables can becontrolled and varied based on temperature monitored at multiple sites,and impedance to current flow that is monitored, indicating changes incurrent carrying capability of the tissue during the ablative process.

Referring now to FIGS. 22(a), 22(b), 22(c), 22 and 24, an RF treatmentapparatus 110 is illustrated which can be used to ablate a selectedtissue mass, including but not limited to a tumor, or treat the mass byhyperthermia. Treatment apparatus 110 includes a catheter 112 with acatheter lumen in which different devices are introduced and removed. Aninsert 114 is removably positioned in the catheter lumen. Insert 114 canbe an introducer, a needle electrode, and the like.

When insert 114 is an introducer, including but not limited to a guidingor delivery catheter, it is used as a means for puncturing the skin ofthe body, and advancing catheter 112 to a desired site. Alternatively,insert 114 can be both an introducer and an electrode adapted to receiveRF current for tissue ablation and hyperthermia.

If insert 114 is not an electrode, then a removable electrode 116 ispositioned in insert 114 either during or after treatment apparatus 110has been introduced percutaneously to the desired tissue site. Electrode116 has an electrode distal end that advances out of an insert distalend. In this deployed position, RF energy is introduced to the tissuesite along a conductive surface of electrode 116.

Electrode 116 can be included in treatment apparatus 110, and positionedwithin insert 114, while treatment apparatus 110 is being introduced tothe desired tissue site. The distal end of electrode 116 can havesubstantially the same geometry as the distal end of insert 114 so thatthe two ends are essentially flush. Distal end of electrode 116, whenpositioned in insert 114 as it is introduced through the body, serves toblock material from entering the lumen of insert 114. The distal end ofelectrode 116 essentially can provide a plug type of function.

Electrode 116 is then advanced out of a distal end of insert 114, andthe length of an electrode conductive surface is defined, as explainedfurther in this specification. Electrode 116 can advance straight,laterally or in a curved manner out of distal end of insert 114.Ablative or hyperthermia treatment begins when two electrodes 116 arepositioned closely enough to effect bipolar treatment of the desiredtissue site or tumor. A return electrode attaches to the patient's skin.Operating in a bipolar mode, selective ablation of the tumor isachieved. However, it will be appreciated that the present invention issuitable for treating, through hyperthermia or ablation, different sizesof tumors or masses. The delivery of RF energy is controlled and thepower at each electrode is maintained, independent of changes in voltageor current. Energy is delivered slowly at low power. This minimizesdesiccation of the tissue adjacent to the electrodes 116, permitting awider area of even ablation. In one embodiment, 8 to 14 W of RF energyis applied in a bipolar mode for 10 to 25 minutes. An ablation areabetween electrodes 116 of about 2 to 6 cm is achieved.

Treatment apparatus 110 can also include a removable introducer 118which is positioned in the insert lumen instead of electrode 116.Introducer 118 has an introducer distal end that also serves as a plug,to minimize the entrance of material into the insert distal end as itadvances through a body structure. Introducer 118 is initially includedin treatment apparatus, and is housed in the lumen of insert 114, toassist the introduction of treatment apparatus 110 to the desired tissuesite. Once treatment apparatus 110 is at the desired tissue site, thenintroducer 118 is removed from the insert lumen, and electrode 116 issubstituted in its place. In this regard, introducer 118 and electrode116 are removable to and from insert 114.

Also included is an insulator sleeve 120 coupled to an insulator slide122. Insulator sleeve 120 is positioned in a surrounding relationship toelectrode 116. Insulator slide 122 imparts a slidable movement of theinsulator sleeve along a longitudinal axis of electrode 116 in order todefine an electrode conductive surface that begins at an insulatorsleeve distal end.

A thermal sensor 124 can be positioned in or on electrode 116 orintroducer 118. A thermal sensor 126 is positioned on insulator sleeve120. In one embodiment, thermal sensor 124 is located at the distal endof introducer 118, and thermal sensor 126 is located at the distal endof insulator sleeve 120, at an interior wall which defines a lumen ofinsulator sleeve 120. Suitable thermal sensors include a T typethermocouple with copper constantene, J type, E type, K type,thermistors, fiber optics, resistive wires, thermocouples IR detectors,and the like. It will be appreciated that sensors 124 and 126 need notbe thermal sensors.

Catheter 112, insert 114, electrode 116 and introducer 118 can be madeof a variety of materials. In one embodiment, catheter 112 is blackanodized aluminum, 0.5 inch, electrode 116 is made of stainless steel,preferably 18 gauge, introducer 118 is made of stainless steel,preferably 21 gauge, and insulator sleeve 120 is made of polyimide.

By monitoring temperature, RF power delivery can be accelerated to apredetermined or desired level. Impedance is used to monitor voltage andcurrent. The readings of thermal sensors 124 and 126 are used toregulate voltage and current that is delivered to the tissue site. Theoutput for these sensors is used by a controller, described further inthis specification, to control the delivery of RF energy to the tissuesite. Resources, which can be hardware and/or software, are associatedwith an RF power source, coupled to electrode 116 and the returnelectrode. The resources are associated with thermal sensors 124 and125, the return electrode as well as the RF power source for maintaininga selected power at electrode 116 independent of changes in voltage orcurrent. Thermal sensors 124 and 126 are of conventional design,including but not limited to thermistors, thermocouples, resistivewires, and the like.

Electrode 116 is preferably hollow and includes a plurality of fluiddistribution ports 128 from which a variety of fluids can be introduced,including electrolytic solutions, chemotherapeutic agents, and infusionmedia.

A specific embodiment of the RF treatment device 110 is illustrated inFIG. 23. Included is an electrode locking cap 128, an RF coupler 310, anintroducer locking cap 312, insulator slide 122, catheter body 112,insulator retainer cap 134, insulator locking sleeve 136, a luerconnector 138, an insulator elbow connector 140, an insulator adjustmentscrew 142, a thermocouple cable 144 for thermal sensor 126, athermocouple cable 146 for thermal sensor 124 and a luer retainer 148for an infusion device 150.

In another embodiment of RF treatment apparatus 110, electrode 116 isdirectly attached to catheter 112 without insert 114. Introducer 118 isslidably positioned in the lumen of electrode 116. Insulator sleeve 120is again positioned in a surrounding relationship to electrode 116 andis slidably moveable along its surface in order to define the conductivesurface. Thermal sensors 124 and 126 are positioned at the distal endsof introducer 118 and insulator sleeve 120. Alternatively, thermalsensor 124 can be positioned on electrode 116, such as at its distalend. The distal ends of electrode 116 and introducer 118 can besharpened and tapered. This assists in the introduction of RF treatmentapparatus to the desired tissue site. Each of the two distal ends canhave geometries that essentially match. Additionally, distal end ofintroducer 118 can be an essentially solid end in order to prevent theintroduction of material into the lumen of catheter 116.

In yet another embodiment of RF treatment apparatus 110, infusion device150 remains implanted in the body after catheter 112, electrode 116 andintroducer 118 are all removed. This permits a chemotherapeutic agent,or other infusion medium, to be easily introduced to the tissue siteover an extended period of time without the other devices of RFtreatment apparatus 110 present. These other devices, such as electrode116, can be inserted through infusion device 150 to the tissue site at alater time for hyperthermia or ablation purposes. Infusion device 150has an infusion device lumen and catheter 112 is at least partiallypositioned in the infusion device lumen. Electrode 116 is positioned inthe catheter lumen, in a fixed relationship to catheter 112, but isremovable from the lumen. Insulator sleeve 120 is slidably positionedalong a longitudinal axis of electrode 116. Introducer 118 is positionedin a lumen of electrode 116 and is removable therefrom. A power sourceis coupled to electrode 116. Resources are associated with thermalsensors 124 and 126, voltage and current sensors that are coupled to theRF power source for maintaining a selected power at electrode 116.

The distal end of RF treatment apparatus 110 is shown in FIG. 22(b).Introducer 118 is positioned in the lumen of electrode 116, which can besurrounded by insulator sleeve 120, all of which are essentially placedin the lumen of infusion device 150. It will be appreciated, however,that in FIG. 22(b) insert 114 can take the place of electrode 116, andelectrode 116 can be substituted for introducer 118.

The distal end of insulator sleeve 120 is illustrated in FIG. 22(c).Thermal sensor 126 is shown as being in the form of a thermocouple. InFIG. 22(d), thermal sensor 124 is also illustrated as a thermocouplethat extends beyond a distal end of introducer 118, or alternative adistal end of electrode 116.

Referring now to FIGS. 25(a) and 25(b), infusion device 150 is attachedto the distal end of catheter 112 and retained by a collar. The collaris rotated, causing catheter 112 to become disengaged from infusiondevice 150. Electrode 116 is attached to the distal end of catheter 112.Catheter 112 is pulled away from infusion device 150, which also removeselectrode 116 from infusion device 150. Thereafter, only infusion device150 is retained in the body. While it remains placed, chemotherapeuticagents can be introduced through infusion device 150 to treat the tumorsite. Additionally, by leaving infusion device 150 in place, catheter112 with electrode 116 can be reintroduced back into the lumen ofinfusion device 150 at a later time for additional RF treatment in theform of ablation or hyperthermia.

In FIG. 26(a), electrode 116 is shown as attached to the distal end ofcatheter 112. Introducer 118 is attached to introducer locking cap 132which is rotated and pulled away from catheter 112. As shown in FIG.26(b) this removes introducer 118 from the lumen of electrode 116.

Referring now to FIG. 27(a), electrode 116 is at least partiallypositioned in the lumen of catheter 112. Electrode locking cap 128 ismounted at the proximal end of catheter 112, with the proximal end ofelectrode 116 attaching to electrode locking cap 128. Electrode lockingcap 128 is rotated and unlocks from catheter 112. In FIG. 27(b),electrode locking cap 128 is then pulled away from the proximal end ofcatheter 112, pulling with it electrode 116 which is then removed fromthe lumen of catheter 112. After electrode 116 is removed from catheter112, insulator sleeve 120 is locked on catheter 112 by insulatorretainer cap 134.

In FIG. 28(a), insulator retainer cap 134 is unlocked and removed fromcatheter 112. As shown in FIG. 28(b), insulator sleeve 120 is then slidoff of electrode 116. FIG. 28(c) illustrates insulator sleeve 120completely removed from catheter 112 and electrode 116.

Referring now to FIGS. 29(a) and 29(b), after introducer 118 is removedfrom catheter 112, a fluid source, such as syringe 151, delivering asuitable fluid, including but not limited to a chemotherapeutic agent,attaches to luer connector 138 at the proximal end of catheter 112.Chemotherapeutic agents are then delivered from syringe 151 throughelectrode 116 to the tumor site. Syringe 151 is then removed fromcatheter 112 by imparting a rotational movement of syringe 151 andpulling it away from catheter 112. Thereafter, electrode 116 can deliverfurther RF power to the tumor site. Additionally, electrode 116 andcatheter 112 can be removed, leaving only infusion device 150 in thebody. Syringe 151 can then be attached directly to infusion device 150to introduce a chemotherapeutic agent to the tumor site. Alternatively,other fluid delivery devices can be coupled to infusion device 150 inorder to have a more sustained supply of chemotherapeutic agents to thetumor site.

Once chemotherapy is completed, electrode 116 and catheter 112 can beintroduced through infusion device 150. RF power is then delivered tothe tumor site. The process begins again with the subsequent removal ofcatheter 112 and electrode 116 from infusion device 150. Chemotherapycan then begin again. Once it is complete, further RF power can bedelivered to the tumor site. This process can be repeated any number oftimes for an effective multi-modality treatment of the tumor site.

Referring now to FIG. 30, a block diagram of power source 152 isillustrated. Power source 152 includes a power supply 154, powercircuits 156, a controller 158, a power and impedance calculation device160, a current sensor 162, a voltage sensor 164, a temperaturemeasurement device 166 and a user interface and display 168.

FIGS. 31(a) through 31(g) are schematic diagrams of power supply 154,voltage sensor 164, current sensor 162, power computing circuitassociated with power and impedance calculation device 160, impedancecomputing circuit associated with power and impedance calculation device160, power control circuit of controller 158 and an eight channeltemperature measurement circuit of temperature measure device 166,respectively.

Current delivered through each electrode 116 is measured by currentsensor 162. Voltage between the electrodes 116 is measured by voltagesensor 164. Impedance and power are then calculated at power andimpedance calculation device 160. These values can then be displayed atuser interface 168. Signals representative of power and impedance valuesare received by controller 158.

A control signal is generated by controller 158 that is proportional tothe difference between an actual measured value, and a desired value.The control signal is used by power circuits 156 to adjust the poweroutput in an appropriate amount in order to maintain the desired powerdelivered at the respective electrode 116.

In a similar manner, temperatures detected at thermal sensors 124 and126 provide feedback for maintaining a selected power. The actualtemperatures are measured at temperature measurement device 166, and thetemperatures are displayed at user interface 168. A control signal isgenerated by controller 159 that is proportional to the differencebetween an actual measured temperature, and a desired temperature. Thecontrol signal is used by power circuits 157 to adjust the power outputin an appropriate amount in order to maintain the desired temperaturedelivered at the respective sensor 124 or 126.

Controller 158 can be a digital or analog controller, or a computer withsoftware. When controller 158 is a computer it can include a CPU coupledthrough a system bus. On this system can be a keyboard, a disk drive, orother non-volatile memory systems, a display, and other peripherals, asare known in the art. Also coupled to the bus are a program memory and adata memory.

User interface 168 includes operator controls and a display. Controller158 can be coupled to imaging systems, including but not limited toultrasound, CT scanners and the like.

Current and voltage are used to calculate impedance. Diagnostics can beperformed optically, with ultrasound, CT scanning, and the like.Diagnostics are performed either before, during and after treatment.

The output of current sensor 162 and voltage sensor 164 is used bycontroller 158 to maintain the selected power level at electrodes 116.The amount of RF energy delivered controls the amount of power. Aprofile of power delivered can be incorporated in controller 158, and apre-set amount of energy to be delivered can also be profiled.

Circuitry, software and feedback to controller 158 result in processcontrol, and the maintenance of the selected power that is independentof changes in voltage or current, and are used to change, (i) theselected power, including RF, ultrasound and the like, (ii) the dutycycle (on-off and wattage), (iii) bipolar energy delivery and (iv) fluiddelivery, including chemotherapeutic agents, flow rate and pressure.These process variables are controlled and varied, while maintaining thedesired delivery of power independent of changes in voltage or current,based on temperatures monitored at thermal sensors 124 and 126 atmultiple sites.

Controller 158 can be microprocessor controlled. Referring now to FIG.31, current sensor 162 and voltage sensor 164 are connected to the inputof an analog amplifier 170. Analog amplifier 170 can be a conventionaldifferential amplifier circuit for use with thermal sensors 124 and 126.The output of analog amplifier 170 is sequentially connected by ananalog multiplexer 172 to the input of analog-to-digital converter 174.The output of analog amplifier 170 is a voltage which represents therespective sensed temperatures. Digitized amplifier output voltages aresupplied by analog-to-digital converter 174 to a microprocessor 176.Microprocessor 176 may be a type 68HCII available from Motorola.However, it will be appreciated that any suitable microprocessor orgeneral purpose digital or analog computer can be used to calculateimpedance or temperature.

Microprocessor 176 sequentially receives and stores digitalrepresentations of impedance and temperature. Each digital valuereceived by microprocessor 176 corresponds to different temperatures andimpedances.

Calculated power and impedance values can be indicated on user interface168. Alternatively, or in addition to the numerical indication of poweror impedance, calculated impedance and power values can be compared bymicroprocessor 176 with power and impedance limits. When the valuesexceed predetermined power or impedance values, a warning can be givenon interface 168, and additionally, the delivery of RF energy can bereduced, modified or interrupted. A control signal from microprocessor176 can modify the power level supplied by power supply 154.

An imaging system can be used to first define the volume of the tumor orselected mass. Suitable imaging systems include but are not limited to,ultrasound, CT scanning, X-ray film, X-ray fluoroscope, magneticresonance imaging, electromagnetic imaging and the like. The use of suchdevices to define a volume of a tissue mass or a tumor is well known tothose skilled in the art.

Specifically with ultrasound, an ultrasound transducer transmitsultrasound energy into a region of interest in a patient's body. Theultrasound energy is reflected by different organs and different tissuetypes. Reflected energy is sensed by the transducer, and the resultingelectrical signal is processed to provide an image of the region ofinterest. In this way, the volume to be ablated is ascertained.

Ultrasound is employed to image the selected mass or tumor. This imageis then imported to user interface 168. The placement of electrodes 116can be marked, and RF energy delivered to the selected site with priortreatment planning. Ultrasound can be used for real time imaging. Tissuecharacterization of the imaging can be utilized to determine how much ofthe tissue is heated. This process can be monitored. The amount of RFpower delivered is low, and the ablation or hyperthermia of the tissueis slow. Desiccation of tissue between the tissue and each needle 116 isminimized by operating at low power.

The following examples illustrate the use of the invention with two RFtreatment apparatus with two electrodes as shown in FIG. 32, or a pairof two electrodes, that are used in a bipolar mode to ablate tissue.

EXAMPLE 1

Exposed electrode length: 1.5 cm Distance between electrodes: 1.5 cmPower setting: 5 W Ablation time: 10 min. Lesion size: width: 2 cmlength: 1.7 cm depth: 1.5 cm

EXAMPLE 2

Exposed electrode length: 1.5 Distance between electrodes: 2.0 Powersetting: 7.0 Ablation time: 10 min. Lesion size: width: 2.8 cm length:2.5 cm depth: 2.2 cm

EXAMPLE 3

Exposed electrode length: 2.5 cm Distance between electrodes: 2.0 cmPower setting: 10 W Ablation time: 10 min. Lesion size: width: 3.0 cmlength: 2.7 cm depth: 1.7 cm

EXAMPLE 4

Exposed electrode length: 2.5 cm Distance between electrodes: 2.5 cmPower setting: 8 W Ablation time: 10 min. Lesion size: width: 2.8 cmlength: 2.7 cm depth: 3.0 cm

EXAMPLE 5

Exposed electrode length: 2.5 cm Distance between electrodes: 2.5 cmPower setting: 8 W Ablation time: 12 min. Lesion size: width: 2.8 cmlength: 2.8 cm depth: 2.5 cm

EXAMPLE 6

Exposed electrode length: 2.5 cm Distance between electrodes: 1.5 cmPower setting: 8 W Ablation time: 14 min. Lesion size: width: 3.0 cmlength: 3.0 cm depth: 2.0 cm

EXAMPLE 7

With return electrode at 1.5 cm Exposed electrode length: 2.5 cmDistance between electrodes: 2.5 cm Power setting: 8 W Ablation time: 10min. Lesion size: width: 3.0 cm length: 3.0 cm depth: 3.0 cm

EXAMPLE 8

Exposed electrode length: 2.5 cm Distance between electrodes: 2.5 cmPower setting: 10 W Ablation time: 12 min. Lesion size: width: 3.5 cmlength: 3.0 cm depth: 2.3 cm

EXAMPLE 9

Exposed electrode length: 2.5 cm Distance between electrodes: 2.5 cmPower setting: 11 W Ablation time: 11 min. Lesion size: width: 3.5 cmlength: 3.5 cm depth: 2.5 cm

EXAMPLE 10

Exposed electrode length: 3.0 cm Distance between electrodes: 3.0 cmPower setting: 11 W Ablation time: 15 min. Lesion size: width: 4.3 cmlength: 3.0 cm depth: 2.2 cm

EXAMPLE 11

Exposed electrode length: 3.0 cm Distance between electrodes: 2.5 cmPower setting: 11 W Ablation time: 11 min. Lesion size: width: 4.0 cmlength: 3.0 cm depth: 2.2 cm

EXAMPLE 12

Exposed electrode length: 4.0 cm Distance between electrodes: 2.5 cmPower setting: 11 W Ablation time: 16 min. Lesion size: width: 3.5 cmlength: 4.0 cm depth: 2.8 cm

EXAMPLE 13

Two pairs of electrodes (Four electrodes) Exposed electrode length: 2.5cm Distance between electrodes: 2.5 cm Power setting: 12 W Ablationtime: 16 min. Lesion size: width: 3.5 cm length: 3.0 cm depth: 4.5 cm

EXAMPLE 14

Two pairs of electrodes (Four electrodes) Exposed electrode length: 2.5cm Distance between electrodes: 2.5 cm Power setting: 15 W Ablationtime: 14 min. Lesion size: width: 4.0 cm length: 3.0 cm depth: 5.0 cm

The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modifications,variations and different combinations of embodiments will be apparent topractitioners skilled in this art. Also it will be apparent to theskilled practitioner that elements from one embodiment can be recombinedwith one or more other embodiments. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. A tissue ablation apparatus, comprising: anelongated delivery device including a lumen; an obturator with a tissuepiercing distal end, the obturator being positionable in the lumen ofthe elongated delivery device; an energy delivery device including aplurality of RF electrodes each with a tissue piercing distal portion,the plurality of RF electrodes (a) being positionable in the elongateddelivery device in a compacted state and preformed to assume a curvedshape when deployed, the plurality of RF electrodes (b) exhibiting achanging direction of travel when advanced from the elongated deliverydevice to a selected tissue site, and (c) defining an ablation volumewhen in said deployed state; at least one of (i) the elongated deliverydevice, or (ii) at least one of the plurality of RF electrodes having aninfusion lumen terminating in at least one infusion port for fluiddelivery therethrough.
 2. The apparatus of claim 1, wherein theapparatus is operable in a bi-polar mode.
 3. The apparatus of claim 2,wherein at least one of the plurality of RF electrodes is configured asa positive electrode.
 4. The apparatus of claim 1, wherein the apparatusis operable in a mono-polar mode.
 5. The apparatus of claim 1, furthercomprising: an insulator positioned in a surrounding relationship to atleast a portion of one of (i) the elongated delivery device, or (ii) atleast one of the plurality of RF electrodes.
 6. The apparatus of claim5, wherein said insulator is slidably positionable over at least one ofthe plurality or RF electrodes to produce a selectable energy deliverysurface.
 7. The apparatus of claim 5, further comprising: a sensorpositioned on the insulator.
 8. The apparatus of claim 7, wherein thesensor is selected from the group consisting of a thermal sensor and anoptical sensor.
 9. The apparatus of claim 1, further comprising: asensor positioned on at least one of (i) the elongated delivery device,or (ii) at least one of the plurality of RF electrodes.
 10. Theapparatus of claim 9, wherein said sensor is positioned at a distalportion of at least one of (i) the elongated delivery device, or (ii) atleast one of the plurality of RF electrodes.
 11. The apparatus of claim9, wherein said sensor is a thermal sensor.
 12. The apparatus of claim9, wherein said sensor is an optical sensor.
 13. The apparatus of claim1, wherein the elongated delivery device includes a tapered distal end.14. The apparatus of claim 1, wherein at least one of the plurality ofRF electrodes has an infusion lumen that terminates at one or moreinfusion ports in the electrode; and wherein said at least one of theplurality of RF electrodes has a proximal end adapted to be operativelycoupled to a source of fluid.
 15. The apparatus of claim 1, wherein theapparatus is configured to have independent fluid delivery to theplurality of RF electrodes.
 16. The apparatus of claim 1, wherein the atleast one infusion port is positioned at one of a distal portion or adistal end of at least one of (i) the elongated delivery device, or (ii)at least one of the plurality of RF electrodes.
 17. The apparatus ofclaim 1, where at least one of the plurality of RF electrodes has aseries of end region infusion ports positioned at the distal end of theat least one RF electrode.
 18. The apparatus of claim 1, furthercomprising a return electrode adapted for contact with a patient's skin.19. The apparatus claim 1, further comprising control means coupled toan RF source for controlling process variables.
 20. The apparatus ofclaim 19, wherein the process variables are at least one of (i) a powerlevel; (ii) a duty cycle; (iii) an energy delivery; (iv) a fluiddelivery flow rate or (v) a fluid pressure.
 21. The apparatus of claim19, wherein the control means includes at least one of: (i) a digitalcontroller, (ii) an analog controller and (iii) a programmed computer.22. The apparatus of claim 19, further comprising an RF source coupledto the plurality of RF electrodes for providing RF energy to the RFelectrodes.
 23. The apparatus of claim 22, wherein said control meansare operatively connected to the plurality of RF electrodes and the RFsource to control application of RF current to the electrodes.
 24. Theapparatus of claim 23, wherein the control means is a feedback controloperatively coupled to a thermal sensor on any one of the plurality ofRF electrodes, and the RF source.
 25. The apparatus of claim 24, whereinthe feedback control adjusts the RF energy delivered to the plurality ofRF electrodes from the RF source.
 26. The apparatus of claim 19, whereinthe control means is a feedback control that adjusts the RF energydelivered to the plurality of RF electrodes from the RF source inresponse to system impedance.
 27. The apparatus of claim 1, furthercomprising an electrode advancement member coupled to the plurality ofRF electrodes, where the advancement member is configured to advance theplurality of RF electrodes out of the elongated delivery device.
 28. Theapparatus of claim 27, wherein the electrode advancement member isrigid.
 29. A tissue ablation apparatus, comprising: an elongateddelivery device including a lumen; an obturator with a tissue piercingdistal end, the obturator being positionable in the lumen of theelongated delivery device; an energy delivery device including aplurality of RF electrodes each with a tissue piercing distal portion,the plurality of RF electrodes (a) being positionable in the elongateddelivery device in a compacted state and being preformed to assume acurved shape when deployed, the plurality of RF electrodes (b)exhibiting a changing direction of travel when advanced from theelongated delivery device to a selected tissue site, and (c) defining anablation volume when in said deployed state, said device being adaptedfor operative connection to a source of RF energy for applying RF energyto said plurality of RF electrodes in said deployed state; and at leastone of (i) the elongated delivery device, or (ii) at least one of theplurality of RF electrodes having an infusion lumen terminating in atleast one infusion port for fluid delivery therethrough.
 30. Theapparatus of claim 29, wherein the infusion port is positioned at one ofa distal portion or a distal end of at least one of (i) the elongateddelivery device, or (ii) at least one of the plurality of RF electrodes.31. The apparatus of claim 29, wherein the apparatus is operable in abi-polar mode.
 32. The apparatus of claim 31, wherein at least one ofthe plurality of RF electrodes is configured as a positive electrode.33. The apparatus of claim 29, wherein the apparatus is operable in amono-polar mode.
 34. The apparatus of claim 29, further comprising: arigid electrode advancement member coupled to the energy deliverydevice.
 35. The apparatus of claim 29, further comprising: an insulatorpositioned in a surrounding relationship to at least a portion of atleast one of (i) the elongated delivery device, or (ii) at least one ofthe plurality of RF electrodes.
 36. The apparatus of claim 35, furthercomprising: a sensor positioned on said insulator.
 37. The apparatus ofclaim 36, wherein said sensor is selected from the group consisting of athermal sensor and an optical sensor.
 38. The apparatus of claim 29,further comprising: a sensor positioned on at least one of (i) theelongated delivery device, or (ii) at least one of the plurality of RFelectrodes.
 39. The apparatus of claim 38, further comprising: a sensorpositioned at a proximal end of the first insulator; and a sensorpositioned at a proximal end of the second insulator.
 40. The apparatusof claim 38, wherein the sensor is a thermal sensor.
 41. The apparatusof claim 29, wherein the first elongated delivery device includes atapered distal end.
 42. The apparatus of claim 29, wherein said sourceof RF energy includes function for having impedance monitored at saidplurality of RF electrodes and controlling RF applied according toimpedance.
 43. The apparatus of claim 29, wherein at least one of theplurality of RF electrodes has an infusion lumen that terminates at oneor more infusion ports in the electrodes; and wherein said at least oneof the plurality of RF electrodes has a proximal end adapted to beoperatively coupled to a source of fluid.
 44. The apparatus of claim 29,wherein the apparatus is configured to have independent fluid deliveryto the plurality of RF electrodes.
 45. The apparatus of claim 29, whereat least one of the plurality of RF electrodes has a series of endregion infusion ports positioned at the distal end of said at least oneof the plurality of RF electrodes.
 46. The apparatus claim 29, furthercomprising control means coupled to the RF source for controllingprocess variables.
 47. The apparatus of claim 46, wherein the processvariables are at least one of (i) a power level; (ii) a duty cycle;(iii) an energy delivery; (iv) a fluid delivery flow rate or (v) a fluidpressure.
 48. The apparatus of claim 46, wherein the control meansincludes at least one of: (i) a digital controller, (ii) an analogcontroller and (iii) a programmed computer.
 49. The apparatus of claim46, further comprising an RF source coupled to the plurality of RFelectrode for providing RF energy to the RF electrodes.
 50. Theapparatus of claim 49, wherein said control means are operativelyconnected to the plurality of RF electrodes and the RF source to controlapplication of RF current to the electrodes.
 51. The apparatus of claim50, wherein the control means is a feedback control operatively coupledto a thermal sensor on any one of the plurality of RF electrodes, andthe RF source.
 52. The apparatus of claim 51, wherein the feedbackcontrol adjusts the RF energy delivered to the plurality of RFelectrodes from the RF source.
 53. The apparatus of claim 46, whereinthe control means is a feedback control that adjusts the RF energydelivered to the plurality of RF electrodes from the RF source inresponse to system impedance.